1. Field of the Invention
The present invention relates to a liquid jet recording head which performs recording by jetting droplets such as recording liquid from a discharge port to a recording medium such as paper and cloth, and a liquid jet recording apparatus which uses the liquid jet recording head, or a manufacturing method of the liquid jet recording head.
2. Description of the Related Art
Such a liquid jet recording apparatus features a recording head which can be easily decreased in size. Further, the apparatus can record a highly fined image at high speed and can decrease running costs and reduce noise since the apparatus is a non impact-printer. Furthermore, the apparatus has many advantages, for example, the apparatus can easily record a color image by using multicolor recording liquid.
The liquid jet recording head includes a recording head which forms the droplets, and a recording liquid supply unit which supplies the recording liquid to the recording head. The apparatus has two types of structures. In one type, a recording liquid storage tank can be exchanged separate from the recording head and in another one the recording head is integrated with the recording liquid storage tank.
A conventional recording head structure of the recording liquid storage tank exchange type will be described.
FIGS. 16A and 16B are perspective views illustrating a recording liquid storage tank mounted on the recording head. FIG. 16C is an exploded perspective view illustrating a periphery of the recording head.
The liquid jet recording head (recording head cartridge H1000) illustrated in FIGS. 16A and 16B includes an ink tank H1900 and a recording head H1001. The ink tank H1900 is detachably held by and secured to the recording head H1001 (Japanese Patent Application Laid-Open No. 2007-283668).
Further, the recording head H1001 holds the ink tank H1900 and a recording element unit H1002 including a recording element substrate H1100 which discharges ink drops by a discharge energy generating element such as an electric thermal conversion element. The recording head h1001 includes a holder unit H1003 which forms an ink flow path for supplying ink to the recording element unit H1002.
FIG. 16C is an exploded perspective view illustrating the recording head H1001. The holder unit H1003 includes a holder H1500 and a flow path forming member H1600, both of which are bonded with each other to, for example, form six flow paths for supplying ink from six ink tanks H1900 to the recording element unit H1002. Ultrasonic wave welding is adopted as a method for bonding the both of the holder H1500 and the flow path forming member H1600. As discussed in U.S. Pat. No. 5,969,738, adhesive may also be used for bonding.
A structure of welding sections is illustrated in FIGS. 17A, 17B, 17C, and 17D. FIG. 17A illustrates a welding surface at a side of the flow path forming member, and FIG. 17B illustrates a welding surface at a side of the holder. FIG. 17C and 17D are cross sectional views taken along line A-A in FIGS. 17A and 17B. FIG. 17C illustrates a state before welding is performed, and FIG. 17D illustrates the state after welding is performed.
As illustrated in the Figures, energy directors H1602 are provided at both sides of a groove, which is to be an ink flow path H1601. The holder H1500 (container holding member) and the flow path forming member H1600 are bonded with each other by the ultrasonic wave welding to complete the ink flow path H1601. Generally, when the ultrasonic wave welding is performed, the energy director is formed on a surface of one of two bonding sections and a clearance groove H1502 for the welding section is formed on a surface of the other one of the two bonding sections so that the base surfaces of the both bonding sections can be in close contact with each other when the ultrasonic wave welding is performed.
If a bubble is generated in or mixed into the recording liquid flowing in a recording liquid supply path of the liquid jet recording head having the structure described above, the droplets are not discharged or unstably discharged. Further, a plurality of flow paths connected to discharge ports has a common liquid chamber at an upper stream side. If the above-described bubbles gather in the common liquid chamber and stay there to grow into a large bubble, defective supplying of the recording liquid can occur. Furthermore, if the defective supplying worsens and spreads in a wide range, the droplets cannot be discharged. As to why the bubble is generated or mixed into the recording liquid, following reasons are conceivable.
1) In order to prevent the recording liquid from leaking out of the discharge port, a negative pressure is maintained in the common liquid chamber at the upper stream side of the discharge port and in the recording liquid supply path. Due to the negative pressure, the air comes through a connection section of the recording liquid supply paths or a minute aperture appearing at a connection section of the common liquid chamber and the recording liquid supply path to become the bubble.
2) The air comes through a member forming the recording liquid supply path or the common liquid chamber, a sealing member connecting between the members, or the adhesive and the sealant to become the bubble.
3) Gas remaining in the a member forming the recording liquid supply path or the common liquid chamber, a sealing member connecting between the members, or the adhesive and the sealant becomes the bubble.
4) Gas remaining melted in the recording liquid generates a bubble along with increase of temperature or decrease of pressure.
5) When the recording liquid is supplied from the recording liquid storage container to the recording head, the bubble is mixed into the recording liquid.
If the above-described bubble stays in the recording liquid supply path or the common liquid chamber, the bubble obtains a ball shape due to a nature of the bubble to keep a surface area thereof small. Accordingly, the more round a cross section of the recording liquid supply path is, the more the supply of the recoding liquid is obstructed. If the recording liquid is hindered from being supplied, eventually the droplet is not discharged due to defective supplying of the recording liquid. Further, even if the droplet is not completely obstructed by the bubble, in a recording mode in which a large amount of recording liquid needs to be supplied, defective discharging of the droplet can occur in a wide range.
Three cases of the conventional structures will be introduced and each of the problems will be described as follows.
In a first case, the flow path forming member and the container holding member are bonded by the ultrasonic wave vibration welding method as discussed in Japanese Patent Application Laid-Open No. 2007-283668. Such a case includes following problems.
1) Due to fusion bonding of two members (liquid path forming member and container holding member), fused resin can get into the recording liquid supply path to form a burr shape and protrusion therein.
2) Further, the protruding resin in a burr shape comes off due to ultrasonic wave vibration and becomes broken pieces, which can scatter in the recording liquid supply path.
3) After the two members are bonded with each other, an inside of the recording liquid supply path needs to be cleaned to remove the burr and the broken pieces.
4) To decrease the protruding of the fused resin, between a raised portion serving as the bonding section of the two members and also as the energy director, and an recessed portion used as the clearance groove into which the raised portion is inserted, a void for containing the fused resin needs to be provided.
5) Since the bubble stays in the void, suction recovery is necessary to remove the staying bubble.
6) A high accuracy of flatness is required of both bonding surfaces of the flow path forming member and the container holding member.
A second case discussed in U.S. Pat. No. 5,969,738 will be described.
The recording liquid supply path discussed in U.S. Pat. No. 5,969,738 has a structure in which a lower portion of the recording liquid supply path has a flat shape and an upper portion has a curved shape of an arc shape as illustrated in FIGS. 18A, 18B, 18C, and 18D, and FIGS. 19A, 19B, 19C, and 19D. This case having the structure described above has the problems described below.
1) If the upper portion of the supply path is formed in an arc shape, a cross-section area of the flow path becomes small, which gives the structure a disadvantage in decreasing size of the recording head.
2) Since recording liquid supply path has the structure in which a circular arc portion 2001 and a flat surface portion 2003 are bonded with each other with adhesive 2004, a void portion 2002 for containing the adhesive 2004 is necessary therebetween.
3) Since a bubble “X” stays in the recessed portion of the void portion 2002 at the lower portion of the flow path, the suction recovery is necessary to remove the bubble.
4) If the structure does not include the void portion 2002, the adhesive 2004 gets into the flow path when the circular arc portion 2001 is bonded with the flat surface portion 2003. Accordingly, the cross-section areas of the flow paths of a plurality of products cannot have a uniform shape.
5) If the adhesive 2004 comes out, wettability inside the flow path cannot be uniform, thus deteriorating a performance in supplying the recording liquid.
6) Since a wall between the adjacent flow paths is formed to have an nonuniform thickness such that the wall becomes thicker toward the upper portion of the flow path, a sink mark can occur when the member is injection molded, thereby deteriorating a dimension accuracy.
7) The high accuracy of the flatness is required of bonding surfaces of the member having the circular arc portion 2001 and the member having the flat surface portion 2003.
The void portion between the above-described arc portion and the flat surface portion is a space having a large flow resistance since the void portion is minute and formed as a recessed portion at a corner of the cross section of the flow path. Further, this void portion exists over a wide range in a direction of a length of the recording liquid supply path.
Therefore, when the recording liquid fills the recording liquid supply path, the bubble tends to remain in this space. The remaining bubble merges with the bubble “X” which is later generated, to grow into a large bubble. Since the bubble remaining in the recording liquid supply path prevents supply of the recording liquid, the bubble needs to be removed as much as possible.
A third case describes a structure in which the container holding member is bonded with the flow path forming member by a laser welding method. This structure has problems described as below.
1) If the flow path portion is irradiated with laser beam, a surface of the flow path is fused, which makes the surface of the flow path coarse. Thus, the flow resistance of the recording liquid is increased to disturb the flow of the recording liquid. Accordingly, widths of the bonding surfaces of the two members need to be set larger than a width of the laser beam to prevent the laser beam from falling onto the surface of the flow path.
2) A change of a thickness of a member at a laser transmission (flow path forming member) side affects a distribution of a laser transmission rate. More specifically, a region having a thick member decreases the laser transmission rate compared to a region having a thin member, thereby decreasing a welding strength.
3) If an obstacle such as a rib, projection, and slope is disposed on the flow path forming member, the laser beam reflects on the obstacle or is refracted. Thus, the distribution of energy of the laser irradiation is deteriorated, and a desired welding strength cannot be obtained.
4) A high accuracy of flatness is required of bonding surfaces of the flow path forming member and the container holding member. If a large curve or a large sink mark is generated on the bonding surfaces, adhesiveness between the container holding member and the flow path forming member is deteriorated.
A material having a large laser transmission rate needs to be selected.
As described in the above three conventional cases, the bubble remaining in the recording liquid supply path may disturb the recording liquid to be supplied. Further, if the bubble grows into a larger bubble, the flow of the recording liquid is disturbed. The recording liquid is not sufficiently supplied into a nozzle, so that the droplet is not discharged.
When the fusion bonding generates the protrusion or a burr into the recording liquid supply path, similarly to the bubble, the protrusion or the burr disturbs the recording liquid to be supplied and causes the droplet not to be discharged. To prevent the droplet from failing to be discharged, the suction recovery processing is necessary. Further, in the laser welding method, changing the thickness of the member and providing the protrusion and the slope that may disturb the laser transmission are restricted.